How the heck does this work?

Go here, and follow the directions. (Just FYI, because it was ambiguous, when she says “remember your number,” she means remember the number that results after you’ve done the subtraction.) I did it five times and she got the right answer five times.

Then, if you can, please explain to me how the heck this works.

Hat tip: Sadie

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No matter what number you pick and do the subtraction if the result is other than nine add the two together and you get 9. On the regift matrix there are nine or is it ten “gifts” that that add up to nine. It is the same gift under each. The next time you try it out they change the gift in those squares appearing to be a different gift every time. Look at the gift in squares 9, 18, 27 etc.

It is not a numerical trick, it is a blue trick. Nearly everyone tries first to click on the number they created, the button to get the answer already has responded to the first click. Try any click on a blue then look at the result.

MacG

Phillips1938 Click on any number that is not 9 or its multiple.

MacG

Just think your number and click done see what happens. Don’t use a multiple of nine and she’ll be wrong every time.

SADIE

I am thoroughly confused (imagine that). I’ve skipped choosing a number and just went to the ‘next’ screen, looked h at a box and she’s right half the time so far.

MacG

Sadie, Don’t do the math 🙂 click the next button to get to the numbers/gifts page. Look at all of the numbered tiles that are a multiple of 9. They are all the same ‘gift’.
The formula works like this: 24-2=22-4=18
25-2=23-5=18
26-2=24-6=18
27-2=25-7=18
28-2=26-8=18
29-2=27-9=18
30-3=27-0=27 so for the 30 series of numbers the answer is the same 27 for all and for the 40 series it will be 36 etc.
This pattern will be true for any two digit number. These numbers 9, 18, 36, 45, 54, 63, 72, 81 are the only answers to her equation for any given two digit number so she puts the same answer in each of those numbered squares. When you try again she changes the re-gift in those numbers.

SADIE

MacG, I like the way you ‘regifted’ the explalnation. Thank you.

Since this is kinda like an open thread gift – has anyone regifted stuff? I haven’t. If the gift was to horrid or worse too small to wear, I just give it away. Thinking about it now … it would make for a small business start-up. You could call it the NEW never REGIFTED Shop of Horrors.

MacG

Sadie, my pleasure. When you give something away it is a gift – it may not be a wrapped fancy new in box present but a gift nonetheless.

I received a book as a gift once from a long time friend that had an inscription to his wife for their 4th anniversary…I never said anything.

Mike Devx

As others have noted, the answer is always a multiple of 9. And in the answer grid, all the multiples of nine have the same “answer”.

Algebraically, you can analyze it like this: A two digit number is 10 times the first digit, plus the second digit.
25 is: 10×2 + 5.
41 is: 10×4 + 1

Algebraically, for any number written as xy: 10x + y

Then she says, subtract the two digits. Well that means subtract x and subtract y. So that becomes:
10x + y – x – y

The plus y and minus y cancel each other out, add to zero. So you’re left with:
10x – x

And that’s 9x. (Nine times the first digit)

9x is always a multiple of nine.

Old Buckeye

I gave away a box of chocolates because I can’t eat chocolate. I didn’t say, “someone else gave me this and I can’t eat it,” but I also didn’t say, “I bought this for you.”

MacG

Mike this is why it took me three years to get through algebra 1-1/2 it is so not intuitive. I followed along till ‘add to zero’ (Maybe you meant ‘add the zero’ but the y’s cancelled out because of their opposing operating symbols so there’s nothing to do, how can you add?) and 10X-X equals 9 not 10. Oh! Oh! MR Kotter! Mr Kotter! 10 exes minus one ex= 9 exes. Just like Elizabeth Taylor! Now I get it! Thanks Mike! I like it!
I was not seeing 10x as a whole number but subtracting the x’s like we did the y’s previously. Maybe someday algebra will make sense if I could figure out those word problems…not the ones in math, the ones in English 🙂

Marica

Note that there are 11 numbers arranged in columns– not very intuitive, numbers are usually arranged in rows, and customarily we put 10 numbers in a row (column).

Still– note the position of the two-digit number you begin with, say, 4th row DOWN. The final answer will be one column to the left, 4th row UP.

This is not an explanation like Mike’s, just an observation. I like patterns.